Method of making blue prints with dark lines and white fields



Patented Dec. 22, 1925.

UNITED STATES 1,566,305 PATENT OFFICE.

ROLAND C. BROWN, OF MILWAUKEE, WISCONSIN.

METHOD or MAKING BLUE PRINTS WITH DARK LINES AND WHITE FIELDS.

No Drawing.

To all whom it may concern Be it known that I, ROLAND 0. BROWN, a citizen of the United States, and a resident of the city of Milwaukee, county of Mil waukee, and State of Wisconsin, have invented certain new and useful Improvements in Methods of Making Blue Prints with Dark Lines and WVhite Fields; and I do declare the following to be a clear, exact, and complete description of the same, suchras will enable persons skilled in the art to which the invention pertains to practice the same.

The invention relates to the art of producing blue-prints of drawings or other sheets having upon the face thereof the delineations and characters which it is desired to reproduce, in multiple copies it may be.

Ordinarily,a tracing of the drawing is made, and this, in the form of a positive, is

" field in dark blue.

imposed upon the surface of a sheet of blueprinting paper and subjected to the action of light rays, with the result that the print appears as a negative or reverse, with the delineations and. characters in white and the Such prints are not highly desirable, but are acceptable in many instances by reason of the great economy with which the results can be'obtained.

Another'method involves the intermediate step of making a negative from the tracing in the form of a brown or Van'Dyke print, which when imposed upon a sheet of blueprinting paper and subjected to the action of light, .will result in a blue-print having dark blue delineations and characters upon a white field. Prints of this nature are much superior to those produced by the practice of the method first described and are highly desired by reason of their clearness, but the performance of the intermediate step of making the Van Dyke negative adds greatly to the cost of production.

My improved process enables me to produce blue-prints of the more desirable class,

r that is, with dark lines and white fields, in a much more expeditious and economical manner.

The practice of my invention involves the use of a sheet of impression or transfer paper, one surface of which is completely coated with a composition of opaque matter, applied but lightly thereto, and adapted to be removed therefrom by the application of pressure exerted upon the other side of the sheet. By means of such pressure, the mat- Application filed November 6, 1923. Serial No. 673,205.

ter of the composition at the points or lines in which the pressure is applied is removed from the impression or transfer sheet, with the result that the opaque transfer sheet is converted into a negative having clear lines and points at the places where pressure was applied and with an unbroken coating over the other portions of its surface. I

The negative thus produced is directly imposed upon a sheet of blue-printing paper and exposed to the action of light, the rays of which pass through the open lines and points and react upon the surface of the blue-printing paper exposed through the negative. The undisturbed opaque coating covering the other portions of the surface of the impression or transfer sheet prevents the light from acting upon other than the indicated portions of the blue-printing paper. As a result, a blue-print is produced on which the dark delineations and characters thereof are emphasized by the surrounding White field. f

Having thus outlined the general nature of my invention, I will now proceed with a description of a specific application of the improved process, and will point out the novel features of the invention in the appended claims.

It being desired to produce blueprint copies of a drawing, I impose an impression or transfer sheet such as described upon a plain sheet of paper, which I term a checking sheet. Upon the impression or transfer sheet the drawing is superposed, and the delineations and characters of the latter are traced by a stylus or other suitable implement. The pressure exerted in the operation of tracing the drawing acts to remove the coating from the opaque impression or transfer sheet in the lines and points of such pressure and transfer such coating to the checking sheet, so as to convert the impression or transfer sheet into a negative in rection of the latter in any necessary particulaigas by subtraction or addition, may be made.

Erasures may be made upon the coated surface of the negative, and the erased portions again coated by the use of a carbon pencil or suitable composition for further tracing. Surplus marks and characters may be eliminated by coating in the same man ner.

After the negative thus produced has been ascertained to be correct, itscoated surface maybe fixed and preserved from damage by spraying thereover a light protecting coating of a suitable hardening liquid, such as white shellac. After being treated in this manner, the negative may be handled without liability to disturbance of its surface or the delineations and marks thereon.

The negative created in the manner described is placed with the blue-printing paper in a printing frame or machine, as usual in making blue-prints, the sensitized blue-printing paper being affected by the rays of light which pass through the open places in the negative, so that a positive blue-print having the most desirable appearance which it is possible to attain in such matters is produced expeditiously and economically. The elimination bymy process of the older practices of making an ink tracing of the drawing and the intermediate Van Dyke negative are material economical advantages which fiowfrom the present invention.v

The drawing may be produced co-incidently in the tracing operation after first superposing a blank sheet of drawing paper upon the coated sheet, or the drawing to be traced may have been previously executed. Ineither case, it is the pressure exerted in the formation of the delineations and characters in one instance, or in following them in the other, that effects the transfer of the coating from the prepared sheet so as to break the surface of the latter and produce the negative.

Having thus described my invention, what I claim and desire to secure by Letters Patentof the United States, is:

1. The process of making a blue-print with dark delineations and characters upon a white field which consists in imposing upon a plain sheet, an impression or transfer sheet provided upon its underside with an opaque coating and superposing a drawing thereon, tracing the drawing to produce upon the plain sheet a replica of such drawing for checking purposes and convert the impression sheet into a negative by the transfer of the coating to the plain sheet in the tracing operation, fixing the coatingupon the negative by applying a preservative thereto, and printing copies upon sensitized paper by passing light rays through the open lines of the drawing.

2. The process of making a blue-print with dark delineations and characters upon a'white field, which consists in arranging a drawing upon a coated opaque impression or transfer sheet, tracing the drawing by pressure to remove the coating of the sheet in correspondence with the traced delineations and characters and convert the coated sheet into a negative of the drawing, fixing the coating upon the negative by applying a perservative thereto, and printing copies upon sensitized paper by passing light rays through the open lines of such negative.

In testimony whereof, I have signed my name at Milwaukee, this 30th day of October, 1923.

ROLAND C. BROWN. 

